Indigo is a very tall man with a clown-like appearance. He has indigo hair, with two particularly large tufts at the side of the head, and his face is white, with purple lines near his eyes, presumably some sort of make-up. He is pot bellied, with thin limbs, and a muscular torso, making his body resemble a Volumetric flask. On his forehead he has a pair of purple round-shaped eyeglasses. He wears a large yellow polka dotted indigo scarf and indigo-striped shoes (similar to Kuro's) that make a farting noise every time he takes a step. He also wears indigo overalls that exposes his chest, with two lines of buttons on the front, and a lab coat over them. On his hands there is a pair of brown gloves. It seems that in his twenty years, he did not change much in appearance, aside from his scarf being orange with a lined pattern, and he did not wear glasses on top of his forehead.
Indigo is a doctor with an eccentric personality: he has a distinct laugh which goes "Piro piro piro", adorns shoes that emit sounds of flatulence whenever walking, not caring if others gets irritated by this, and also often tries to act like a mime, but usually breaks character by suddenly talking, though ironically becomes completely surprised if someone actually understood his charade type speech. He also appears to be careful, as he always carries around a vial of antidote to the Draft disease, just for precaution.
Indigo was at Shiki's side during the Battle in the Edd War, where the Golden Lion Pirates confronted the Roger Pirates. After the battle, he was seen at his captain's bedside, commenting on his positive attitude towards the steering wheel stuck in his head. He then slapped him in a comedic fashion for mistaking himself with a rooster.
It's unknown what happened to Indigo during Shiki's imprisonment in Impel Down, however when Golden Lion broke free of the gaol and reached Merveille, the loyal scientist was one more time at his side, ready to start developing an ambitious project to defeat the World Government: he will develop the SIQ serum from the IQ plants present on the flying island, making Shiki's plan of an army of mutated animals real.
Indigo was briefly seen during the Little East Blue Arc, commenting on Boss having escaped from him, and then reassuring his captain of the plan's guaranteed success.
Indigo was first seen dancing before Nami with Shiki and Scarlet, in the palace's greenhouse. He proudly showed his captain the new development, a bird producing electricity from his feathers, who ended up shocking the three pirates. He spent the major part of the film at his captain's side, miming the most important news before telling him and the onlookers openly; he was quite surprised when Shiki managed to understand the news regarding Nami's attempt to blow up the Daft Green trees just through his miming actions.
During the pirates meeting in the main hall, he was seen serving them something to drink. When the Straw Hat Pirates arrived and Luffy attempted to chase after Shiki, he tried to attack him with a sword, but he was stopped by Zoro. He fought alongside the others until the palace was attacked by the wild animals.
Later Chopper and Usopp manage to find Nami, who has been infected due to overexposure to the Daft Green plants, and start searching for a cure. They reach the palace's laboratory, but wind up running into Indigo, who has such a cure, but refuses to hand it over, preparing to fight the two. Zoro however arrives, and proceeds to battle him. Indigo shows off his Chemical Juggling ability, attacking the swordsman with his chemical orbs, but he's rapidly defeated when Zoro uses his Ashura: Ugui and he loses control of the Chemical Juggling. He was last seen falling unconscious from the sky, together with Shiki and Scarlet, after his captain's levitation control over the islands was broken. His current fate is unknown.
- His English voice actor is the only actor to voice during two different dubs of One Piece. During the 4kids dub, he also voiced Helmeppo and Toto.
- He shares with Caesar Clown both the scientist profession (even if he's a former Marine), the clown theme (Caesar only in the name) and the Seiyu.
- Like many other characters, Indigo has a distinctive laugh, "piro piro piro piro!". "Piro" sounds similar to "Pierrot", a stock character in pantomime, which befits his clown theme. Ironically, Pierrot is deadpan and downtrodden, while Indigo usually has a wide grin on his face.